public interface LList {

   public void insertFirst (int item);
   public Node deleteFirst ();
   public int size();
   public boolean empty ();
   public void traverse ();

}

class Node {

   private int data;
   private Node next;

   public Node () {
     this(0, null);
   }

   public Node (int d) {
     data = d;
   }
  
   public Node (int d, Node n) {
     data = d;
     next = n;
   }

   public void setData (int newData) {
     data = newData;
   }

   public void setNext (Node newNext) {
     next = newNext;
   } 

   public int getData () {
     return data;
   }

   public Node getNext () {
      return next;
   }

   public void displayNode () {
      System.out.print (data);
   }
}

class LinkListADT implements LList {

   private Node first;

   public LinkListADT () {
     first = null;
   }

   public boolean empty () {
     return (first == null);
   }

   public int size () {
      int count = 0;
      Node current = first;
      while (current != null) {
         count++;
         current = current.getNext();
      }
      return count;
   }     

   public void insertFirst (int newData) {      
      Node newFirst = new Node (newData);
      newFirst.setNext(first);
      first = newFirst;
   }

   public Node deleteFirst () {
      Node temp = first;
      first = first.getNext();
      return temp;
   }

   public boolean search (int key) {
      boolean result = false;
      Node current = first;
      while (current != null) {
         if (current.getData () == key) {
            result = true;
            return result;
         }
         else
            current = current.getNext();
      }
      return result;
   }   
      
   public void traverse () {
      System.out.print ("Current list: ");
      Node current = first;
      while (current != null) {
         current.displayNode ();
         System.out.print ("   ");
         current = current.getNext();
      }
      System.out.println ();
   }
}         

class Listex1 {

   public static void main (String[] args) {

     LinkListADT list1 = new LinkListADT ();

     for (int i = 1; i <= 10; i++) {
        list1.insertFirst(i);
        list1.traverse();
     }

     System.out.println ("Number of nodes on the list: " + list1.size());
     
     System.out.println ("Search for 6: " + list1.search(6));
     System.out.println ("Search for 12: " + list1.search(12));

     for (int i = 1; i <= 10; i++) {
        list1.deleteFirst();
        list1.traverse();
     } 
   }
}